1. Technical Field
The present invention relates to a substrate, an electronic device, and an electronic apparatus.
2. Related Art
Heretofore, electronic devices in which a functional element, such as a gyro element, and an IC (Integrated Circuit) chip which performs the driving or the like of the functional element are disposed within a casing have been known. The electronic device has external mounting terminals on a rear surface of the casing, and is mounted on a mounting board via the external mounting terminals (refer to JP-A-2009-99665 (Patent Document 1)).
On a rear surface of a ceramic package of Patent Document 1, main electrode patterns and sub-electrode patterns are formed as external mounting terminals. Mounting of the ceramic package on a mounting board is performed by bonding the main electrode patterns and the sub-electrode patterns with the mounting board via solder.
The mounting board is usually composed of a glass epoxy board or the like and different in coefficient of thermal expansion from the ceramic package. Therefore, in a state where the ceramic package is mounted on the mounting board, stress acts, with temperature rising, on the interface between the solder and the external mounting terminal.
As shown in FIG. 11, portions on which the stress acts most greatly in the ceramic package of Patent Document 1 are places of the sub-electrode patterns formed at corner portions, the places being indicated by reference signs M (places most separated from a center O′ of a circle circumscribing the four sub-electrode patterns).
However, in the ceramic package of Patent Document 1, since the place indicated by the reference sign M is a “point”, the stress acts concentratedly on the place, resulting in a problem that a crack beginning at the place occurs in the bonding material (solder).